This invention pertains generally to crystal regulated oscillators, and more specifically to crystal oscillator packaging.
Quartz crystal based oscillators are used for generating frequency reference signals in radio telephones and pagers. The reference oscillator signal is typically used by other frequency synthesizers within the mobile radio device with phase locking.
Quartz crystal resonators offer several comparative advantages; they are inert, relatively power efficient, frequency stable and size scalable. However advantageous, crystal resonators present some practical problems. When quartz crystal is manufactured in an economical manner, its resonant frequencies cannot be predicted (or controlled) with an accuracy sufficient for many applications. Furthermore, the oscillating frequency of known quartz crystals is temperature dependantxe2x80x94the sensitivity varying according to crystal cut and crystal quality generally.
Accordingly, crystal oscillator circuits are both factory tuned to account for manufacturing variances and also equipped with features for temperature compensation. In the basic circuit design, an inverter and biasing resistor are each connected in parallel with the crystal resonator. The inverter and biasing resistor serve to start and then maintain the oscillation. An adjustable capacitance element such as a varactor is connected to the quartz crystal to allow frequency adjustment for factory tuning and temperature compensation. A voltage responsive temperature-sensing element is scaled and operably connected to the adjustable capacitance element to provide temperature compensation of the oscillator frequency. This frequency adjustment is conventionally called xe2x80x9cwarpingxe2x80x9d or xe2x80x9cpulling.xe2x80x9d
Radio handsets, pagers and related mobile communicating devices are produced in automated factories in mass volumes. The associated market favors smaller designs and consumer-level pricing. Towards these objectives rigorous attention is applied to electronic component costs and sizes. Therefore, cost and size constraints are important factors in crystal oscillator design.
Because even dust-sized contamination of crystal resonators affects crystal resonance frequencies, packaging and handling for crystal oscillator components is critical. Higher quality crystal based oscillators are assembled in clean room environments, where the crystal resonator is set in a sealed chamber of the overall oscillator package. Inert, dust-free atmospheres are created in the sealed crystal resonator chamber. These special packaging and handling requirements not only contribute to the cost of manufacturing oscillator components but also limit efforts at reducing the overall package size.
There remains a need for lower cost crystal oscillator manufacturing methods and resulting component.
The invention is a crystal-controlled oscillator packaging system. The oscillator has a crystal resonator, and a housing enclosing the resonator. Electrical connectors extend from the crystal resonator through the housing. A wiring substrate has a cavity enclosed by the crystal resonator housing. Electrical oscillator components located within the cavity are electrically coupled to the crystal resonator electrical connectors and form a frequency controlled oscillator circuit therewith. Electrical terminations couple the frequency controlled oscillator circuit with an external electrical circuit.
Another aspect of the invention is a printed wiring board supporting at least one oscillator component. The wiring board has an electrically insulating base layer, and also has an electrically insulating top layer with an opening (or aperture). The oscillator component is supported upon the base and is accessible through the top layer aperture. Electrical wiring electrically couples the oscillator component to the top layer, and resonator package electrical coupling and mounting pads formed on the top layer are capable of operatively electrically connecting a resonator package to the oscillator component.
A preferred embodiment of the invention includes an array of at least two frequency controlled oscillators that is tested as a single unit. A circuit board electrically connects the array of frequency controlled oscillators to a test connector that is operative to couple to a testing computer. Individual ones of the frequency controlled oscillators each have: a cavity within the multi-layer circuit board; a component mounting pad located within the cavity between circuit board top and bottom; a frequency control component adjacent the cavity and forming an enclosure therewith; and an electronic oscillator component with the enclosure.
The invention also includes a printed circuit oscillator wiring array for use in the production of frequency controlled oscillators. A circuit board has electrical connections for connecting an array of at least two frequency controlled oscillators to a test connector that is operative to couple to a testing computer. Individual oscillator wiring circuits within the printed circuit oscillator wiring array each have a cavity within the circuit board; a component mounting pad located within the cavity between circuit board top and bottom; and an electronic oscillator component mounted adjacent the component mounting pad.
In a method aspect of the present invention a multi-layer wiring board substrate is formed with a plurality of cavities. A base-layer wiring substrate having a top and a bottom surface is provided and patterned with electrically conductive traces. A cavity-layer substrate is provided having a plurality of openings defined therein. The cavity-layer substrate is also patterned with electrically conductive traces. The conductive traces include test connectors on the cavity-substrate. The cavity-layer substrate and the base-layer substrate are laminated together to form a laminated, electrically interconnected wiring substrate such that the cavity-layer and the base-layer together define a plurality of cavities. The cavities of the laminated, electrically interconnected wiring substrate are populated with electronic components. A plurality of packaged frequency control components is provided and used to enclose the cavities to produce a plurality of crystal regulated oscillators. The plurality of crystal regulated oscillators is singulated from a balance of the laminated substrate.